OS and In Vitro Infertility

Reactive oxygen and nitrogen species that lead to OS have a negative impact not only on male fertility in natural conception but also on assisted reproductive technologies (ART) in an in vitro setting. In any ART procedure, there is a risk of oxidative damage from sources such as exposure to ambient air [70]. Other sources of OS in an ART setting include the oocyte, embryo, cumulus cells, and immature sperm cells [6]. In addition, spermatozoa used in any ART procedure originate from an environment conducive to OS, which can lead to DNA damage [71].

Studies have shown that the ROS levels in the seminal fluid correlate with fertilizing potential and the IVF rate in procedures such as intrauterine insemination (IUI), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI) [71, 72]. Also, high ROS levels in day 1 embryo culture media have been related to decreased blastocyst and cleavage rate, low fertilization rate, and increased embryo fragmentation in ICSI cycles. Consistently, high day 1 ROS levels in culture media have been correlated with decreased pregnancy rates in ICSI and IVF [73].

ROS production and sperm DNA damage are associated with apoptosis [ 3], which has been shown to be associated with a decrease in fertilization rate [74]. It is of importance to note that sperm with DNA damage has the potential to lead to poor embryo development and carries the risk of birth defects [14]. Miscarriage rates were found to be higher in ICSI than in IVF, which may be explained by the fact that in the ICSI procedure, there is a greater chance of DNA damaged sperm being injected into the oocyte [75]. DNA damaged sperm is less likely to be used to fertilize an oocyte in IVF or IUI because of associated damage to the sperm plasma membrane, which is necessary for fertilization [1].

The general sources, mechanisms, and consequences of OS on male fertility are summarized in Fig. 24.1. Clinical conditions related to OS include idiopathic infertility, leukocytospermia, varicocele, genitourinary tract infection, environmental and lifestyle factors. OS acts through several mechanisms that lead to subfertility, such as lipid peroxidation, DNA damage, and apoptosis. OS can lead to several consequences related to male fertility, both in an in vivo and in vitro setting.

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